The invention relates to method for evaluating two scattered-light signals of an optical hazard detector operating according to the scattered-light principle.
The invention further relates to an optical hazard detector with a detection unit operating in accordance with the scattered-light principle and with an associated electronic evaluation unit.
Furthermore it is generally known that particles with a size of more than 1 μm primarily involve dust, while particles with a size of less than 1 μm primarily involve smoke.
Such a method or such a hazard detector is known from international publication WO 2008/064396 A1. In the publication, for increasing the sensitivity for the detection of smoke particles, it is proposed that the second scattered-light signal be evaluated with blue light wavelength, if the amplitude ratio corresponds to a particle dimension of less than 1 μm. If on the other hand the amplitude ratio corresponds to a particle dimension of more than 1 μm, the difference is formed between the second scattered-light signal with blue light wavelength and the first scattered light with infrared wavelength. The differentiation inhibits the influence of dust and thus largely suppresses the triggering of a false alarm for the presence of a fire.